HIGHLY DISPERSED RHODIUM PARTICLES ON SIO2 AND BETA-FEOOH SUPPORTS FORMED BY PHOTOCHEMICAL DECOMPOSITION OF A RH(I) COMPOUND

The preparation of 2-4-nm-sized Rh particles dispersed on amorphous SiO2 and crytalline beta-FeOOH at room temperature by photochemical decomposition Of [(C2H4)2Rh(OEt)]2.H2O is described. Tetrahydrofuran solutions of the Rh precursor containing either 250 nm sized SiO2 spheres or 250 X 55 nm single-crystal beta-FeOOH rod-shaped particles were irradiated for 3 h with a Hg arc lamp. Transmission electron microscopy, energy dispersive spectroscopy and electron diffraction revealed that 2-4-nm-sized crystalline Rh particles were dispersed on the surface of the metal oxide particles with a Rh weight loading which corresponded closely to the solution Rh content. A series of control experiments in which the rate of photochemical decomposition Of [(C2H4)2Rh(OE)]2.H2O was monitored by H-1 NMR spectroscopy revealed that the precursor reacted in homogeneous solution rather than on the surface of the metal oxide. This represents a convenient method for the preparation of highly dispersed catalyst particles on thermally sensitive substrates.